Electrical tube-immersion heater



March 2l, 1950 w. B. sMlTs ET AL ELECTRICAL TUBE-IMMERSION-HEATER Filed Aug. 15, 1946 Patented Mar. 21, 1950 `ELECTRICAL"TUBE-IIVIMERSION HEATER .WSitzecBeSie Smitsr'Amsterdam, Netherlands, .and .=J ames M. Beck, Birmingham, Ala.

vApplication August 15, 1946,"Serial No. 691,086

(ctms- 41) ..8 Claims.

The object=of`our invention is to provide an electrical tube-immersion heater with veryeffective'hea't transmission and of great durability and `to avoid the drawbacks land `the difficulties inthe manufacture and inthe-use oiknown'constructions.

' Said inventionprincipallyV consists inthe construction Yand arrangement f of `the Aheating Velements. A further'objectof theinventionlis'to provide pressure `r-.'1eans'"for `pressing the heating elements equally against the' outer i tube.

-The invention Afurtl'ier consists 1in I certain Ide tails-oi construction -andfarrangement wof parts as will be hereinafter more particularly'described and claimed.

Referring tothe-accompanying drawing, which forms a part of the specication anden-which similar reference characters indicate similar parts, Figure A1 a y:vertical longitudinal section along the line I-`I of-Fig. 2. `liig. Ziis a top-plan vView. Fig. 3 is a 4vertical longitudinal fsection along the line III-`IIIof1Fig- 2. VVFigat is a cross- `section along'rthelineIV--IV olf-Fig. 3. k'IF-ig. 5 is a 1 horizontal transverse` section Lalong f vthe line V-V oi-Fig. 1. :Fig 6 is asideelevation of apreferred formfof rtheheating. element, `showing this element-ina ati.condition,betore inserting it into thettube. 'Fig 'l f-is VVa'fverticalsectionraalong the' line VII-VII of Fig,16. Figures Band 9-vshow on an enlarged sealer plan i views*l ofthe pressure body .before expandingzandater 'having been expandedbye. pressureV pin. llligures IO-and'l'll are like.viewsv'oialmodication. V.Fig `I2.is an elevation `of the. pressure. pin.

Refer-ringto*the-drawings I isa :cylindrical tube in the usual :outside :form of electrical Stube-irnmersion-heaters. Inside 'of tube 1I ..there-1are a mica. layer .2 .and '-a `bottom disk 22a .of rmica :as :outside insulation. Then follow concentrical'ly from the outside towards the axis ofthe tube the heating 1. element :.3, .a f vfurther insulationelayer lI fand .al hollow `cylindrical pressurecbodys. .This .pressure .bodyis lexpanzdedwthroughza .pressure .pin

I8, as will .bedescribed .later on. Therebyfthe insulating: 4material zandpthe .heating .element :are pressed equallyagainst v.tlfietubel .I l over .the whole width of the element.

The. heat elementfshownconsists. .ofI founsmall individual .elements .a, lb, c, id, which in a* preferred formarelconnectedin parallel. Eachcof these small elements has a narrow mcastrip V6 woundfwithua.thinlheatingl-Wire'l, the ends of which lie yin .notches .8 of.v thelstrips. VAt;the.posi tions of-'the*notches-8,l-a.loop .9 ofiiat wire-is klaid all rou-nd the ends of .theistripsfand .islspot .55

Welded together at points ID nearthefstrips. To the free endso the loops 9 the current supply wires I2 are spot welded. `By this construction the single elements are held at exact distance fromleachother andan unwrenchable unit'of the elements is obtained. Besides thatthe current supply wires cannot slide olic the'elements.

fA special new construction `was necessary-for Vthe pressure body 5. Sli one chooses springlilie pressure means .the elasticity rwould be. eliminated due to -the heating of the elements. Therefore a hollow split cylinder is chosen, :which cylinder isfexpanded `by a cylindrical pressure pin iorced between the rims of the cylinder. The hollow cylinder shown especially in Figures .Sand -9 `is formed from a thin ironsheet. The .thicknesszof the sheet isy important for the quality of the pressure and depends upon the diameter on which the pressure is applied. Is the sheet-too thin it can `easily crackat one point, ifv chosen too thick '.too

much power must beapplied to expand the cylinder.

From the splitrI3 of the cylinder 5 the ends. of the sheet are directed -as flanges I4, I.5'towards the axis of the cylinder. The inner `ends of these flanges are 4supported the one against-the other. To this purpose the `end of one ange, for example, iiangey I5,\is bent'to'form a groove I6 which receives theend of the other flange. The

Aflanges are further bent to form a groove IIfor inserting the cylindrical pressure pinIB. .Figure 8 shows the pressure cylinder previous to tti-ng, and Figureg shows'it expanded by the pressure pin. When pressing the pressure pin in the inner ends ofthe flanges :cannot yield and thereiore the pressure is exertedat the circumference .of the. cylinder, whereby the pressure body puts .the heating .element as well as the insulations under an equal concentric pressure.

Figures 10 and 11 `show .a modified `pressure body constructionwith the same eiect andthe manufacturing speciality that-these cylinderscan be obtained `by ysawing off athinawalled special drawn .prole tube. Here, a continuous tube `5a is `used having radialllyinwardly extendingflanges Maand Iaiormedwith matchinggrooves Ila.

The following advantages are obtained "by the described construction of the heating element and the pressure means.

By dividing the heating element vinto a plurality, for example four individual elements, ,each .of

.these elements is very small, so that v.thestress by the expansion and the ,contraction .of the heating wire is decreased, asthe distance .between two crackpoints of the `wire-Winding .is .only

3 small. Therefore the durability of the heating element is very much increased.

The small elements are wound with a thin heating-wire, which has the advantage, that a thin wire can be more easily subjected to over-loading, due to current-variations, than a thick wire. There is also the low cost for the thin wire in comparison to other constructions which need a greater amount of metal.

A direct heating contact with the heating wire is obtained through the pressure body pressing the heating elements against the outside tubing, thus giving following advantages:

(a) The well cooled heating wire can more safely be subjected to an overloading and can `from the beginning carry a higher current supply.

(b) The heating wire need, not be brought to such a high temperature that the produced heat is mainly given off through radiation. This increases a great deal the durability.

(c) Advantage (b) means that the insulation is heated to a lower degree and can be applied thinner and cheaper.

(d) The thinner insulation affords a better heat transmission between heating wire and outside tubing which in turn gives the advantage of a cooler heating wire.

As there is nothing inside of the immersionheater besides the thin hollow pressure body no heat can be otherwise conducted and all oi the produced heat flows to the outside whereby a very high eiiiciency is reached.

Should one of the small parallel connected heating elements burn out, there are still for instance three more in operation. Through this construction the immersion-heater can be still used although its efficiency is decreased 25%.

A repair of the immersion-heater is possible without diiliculties and at low costs. The pressure-pin is drawn out, a new heating element is inserted and the pin replaced.

The pressure pin (see Fig. 12) has at its one end a point I9 which fits into the groove II of the unexpanded pressure body 5 (see Fig. 8). That point passes over to the cylindrical pin by a small conical part, in order to expand the body 5 more easily. At its other end the pressure pin I8 has a threaded projection 2U, with which the pin can be screwed into a long rod having inside-threading, so that after the complete heating element has been inserted into the tube I, the pressure pin I8 can be easily inserted. In case of repairing the pin I8 can be removed by means of this rod and the heating element drawn out.

Into the upper end of the tube I an insulating l piece 2l is inserted, and tightened and sealed by a small rubber ring 22. The piece 2l is attened at one side as at 23 (see Fig. 4). A holding hook 24 for engaging the rim of a container is inserted into a positioning slot 25 of the upper rim of the tube I. This hook has its inner lower end bent and this bend 26 engages a notch in the flattened side of the piece 2|. In this way the insulating piece 2l is held in a determined position and at an always equal determined distance from the inserted heating-element. Over a trunnion 21 of the piece 2l a handle 28 is shoved. By three screws 29 the handle and the piece 2l aie held in place in the tube and the holding-hook is held against outward movement by the handle. The current-supply-wires I2 are subjected shortly above the heating element to a sharp bend 30 over which a tubular spacer 3I of porcelain, glass or similar material of a chosen length is placed, which tubular piece in turn sets against the insulating piece 2l. The current-supply-wlres I2 being conducted through the tubular piece 3|, which has an insulating core, and through bores of the insulating piece 2I and are connected with the cable 32 in one of the usual ways within the hollow handle 28. Despite the simplicity of this fitting, the relief of tensile stress is so etiicient that it is impossible to pull the current-supplywires out and thereby to damage the heating element.

Pressure body 5. heating element 3 and insulating layers 2, 4 are inserted into the tube I at the same time and in such a manner that the joints of all these parts meet exactly at a place below the cut 25 in the tube. As the insulating piece 2l is held by means of the fastening hook 24 always in the same position no turning and consequently no touching of the current-supply wires is possible.

If the pressure cylinder 5 is expanded by inserting the pressure pin I8 the split or gap of the cylinder becomes broader. This gap has no disadvantageous e`ects as to the heat transmission oi' the heating element, as it is placed due to the above mentioned fitting at a point where no heating wire is present. At the places where heat is to be transmitted, an entirely equal pressure and therewith an equal heat transmission are assured by thus positioning tne parts.

We prefer, as mentioned above, to connect the small individual elements in parallel, but in order to have an immersion-heater ior various voltages the individual elements can be connected either in parallel or in series.

Having thus Iully described our said invention, what we claim as new, and desire to secure by Letters Patent, is:

l. An electrical tube-immersionheater, consisting ol' a cylindrical tube, a plurality of small heating elements within said tube, leach ol' said elements having a narrow strip wound with thin heating wire and with small notches near its ends, in which notches the ends of the heating wire are held, a wire-loop embracing the ends of the strips and spot welded near the strips, means pressing the elements equally against the tube and means for adjusting the parts in the tube.

2. An electrical tube-immersion-heater, consisting of a cylindrical tube, a plurality o small heating elements within said tube, a hollow pressure cylinder within the elements, said cylinder being split longitudinally, a cylindrical pressure pin expanding the cylinder circumferentially and means for adjusting the parts within the tube.

3. An electrical tube-immersion-heater, consisting of a cylindrical tube, a plurality of small heating elements within that tube. a hollow pressure cylinder within the elements, said pressure cylinder having a longitudinal split and flanges extending inwardly towards the axis of the cylinder, the inner ends of these flanges are supported the one against the other a cylindrical pressure pin inserted between said flanges, and means for adjusting the parts in the tube.

4. An electrical tube-immersion-heater according to claim 3, the pressure body being a cut-piece of a special profile-tubing.

5. An electrical tube-immersion-heater according to claim 2, the pressure pin having a small point at one end and a screw projection at the other end.

6. In an electrical tube-immersion-heater the combination of a cylindrical tube, a plurality of narrow heating elements within the tube, means pressing the elements equally against the tube,

into said slot and serving as a guiding point in' assembling the parts.

7. In an electrical tube-immersion-heater the combination of a tube, a plurality of narrow heating elements within the tube, means pressing the elements equally against the tube, an insulation piece extending into the upper end of they tube, a spacing piece between said insulating piece and the heating elements, and current-supply-wires passing through said pieces and connected to said heating elements.

8. In an electrical tube-immersion-heater the combination of a tube, a plurality of small heat- 1 ing elements within the tube, means pressing the elements equally against the tube, an insulation piece arranged at the upper end of the tube, current-supply-wires passing through separated bores of said piece, a holding hook attached to the tube which hook holds the insulation piece in a settled position, and a handle fastened to the tube and overlapping the holding hook to hold it in position.

WYTzE BEYE SMITS. JAMES M. BECK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 755,659 Hathaway Mar. 29, 1904 1,477,602 Simon Dec. 18, 1923 1,674,488 Tang June 19, 1928 2,060,644 Stiebel Nov. 10, 1936 FOREIGN PATENTS zo Number Country Date 243,784 Great Britain Nov. 30, 1925 

